Changed my motherboard and lost my windows key

I just replaced my motherboard recently. When I turned my pc on, windows apparently wasn't activated anymore. I went to the activation settings, then chose "I recently replaced hardware". Windows said that I couldnt activate my copy of windows. This is the second time I replaced my motherboard, but the first time I replaced it I was still able to keep my activated copy of Windows. Is there anything I can do to still activate windows or do I have to buy another key?

If you have the full Home or Pro liscense of windows you should be able to reuse your key as many times as you wish. If it's an OEM liscense (Installed on a prebuilt system like a Dell or HP), you can only use THAT key with THAT motherboard, and will ask you to register a new liscense when you change motherboards.

I built the PC myself, so not oem. When I try to activate windows using my old key, it says that my key is being used in another device. What's weird is that this didn't happen the first time I replaced my m0b0.

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